1. Field of the Invention
This invention relates to a keyboard device of an electronic keyboard musical instrument which has a simple construction, can be produced easily and can provide a stable key pressing operation.
2. Description of the Prior Art
A keyboard device such as the one shown in FIG. 6 of the accompanying drawings, for example, is known as a keyboard device of conventional portable electronic musical instrument, or the like. As shown in the drawing, each key 1 is equipped with a thin and flat hinge portion 2 at its rear end (on the right side in the drawing) and a plurality of keys 1 are integrally molded from a synthetic resin and fitted to the rear part of the upper surface of a chassis 3. A buffer material 4 such as a felt is bonded to both upper and lower surface of the chassis 3 on the foreground side (on the left side in the drawing) so that the lower limit position is restricted by the contact between this buffer material 4 and the lower surface on the back of the keys 1, and similarly, the upper limit position is restricted by the contact with a stopper 5 that is suspended and bent downward. Furthermore, switch supports 6 push a keyboard switch 7 fitted to the back of the chassis.
However, the keyboard device described above does not have any particular means for restricting the transverse shake or vibration of each key 1 and its push-down direction which are barely restricted only by molding accuracy of the hinge portions 2 of the keys 1. Accordingly, the conventional keyboard device involves the problems that if molding accuracy is low or if adjacent keys 1, 1' come into mutual contact due to the change with time and the keys 1 are inclined as shown in FIG. 7, the key arrangement on the upper surface of the keyboard goes out of order, appearance of the keyboard drops as a whole and noise is generated during the key pressing operation.
Further, it is difficult to bond linearly the buffer material 4 having as much a length as required for the arranged keys to the chassis 3 in the key arrangement direction and since the buffer material 4 must be bonded to both upper and lower surfaces, this bonding work is extremely troublesome and time-consuming. Another problem is that if a cantilever support structure is employed for the printed board 7, only one of its sides is supported and consequently, the printed board undergoes deflection as the switch support 6 is lowered by pressing operation of the keys 1. Accordingly, a normal switch operation cannot be obtained. If the printed board 7 is fixed at its front and rear portions, the number of necessary screws increases and the number of man-hours for assembly increases as much.